Checks on the consistency of the information supplied by the different measurement means are necessary to monitor the integrity of the data.
These checks are performed by the user systems (for example the flight management system) according to their various needs in terms of integrity.
The user systems are systems which use, among other things, inertial data or air data. Among the most critical user systems, there are the display system (manual piloting and monitoring of the automatic piloting), automatic pilot (PA) and flight controls (flight control system). There are also the alarm management system (known as flight warning system), the management of the engines, the braking management system, the surveillance system (weather radar, ground collision prevention, airplane collision prevention), the flight recorders and other systems even more functionally distant (such as the air conditioning, the passenger cabin video system, etc.).
This implies that certain systems use information that is deemed unusable by other systems. Consequently, this can lead to situations prejudicial to the safety of the flights, in cases of malfunction, detected or not, of one or more measurement means.